This disclosure relates generally to integrated circuits, and, in particular, to a stacked integrated circuit assembly.
Technological advances have enabled the integration of many electronic components into a single integrated circuit. For example, a modern integrated circuit may contain millions of transistors. Traditionally, an electronic circuit was constructed of a number of discrete electronic components such as discrete transistors. Each discrete electronic component was connected by electrical conductors such as wires or circuit board traces. Today, one or more electronic circuits may be integrated into a single integrated circuit. The integrated circuit contains each electronic circuit's electronic components as well as its connecting electrical conductors. Frequently, an integrated circuit contains many complex electronic circuits. Examples of integrated circuits include computer microprocessors and memory chips.
Implementing an electronic circuit using an integrated circuit may offer a number of advantages over implementing the electronic circuit using discrete electronic components. First, the electronic circuit may require significantly less space on a circuit board when implemented by an integrated circuit than when implemented by discrete parts. This space savings is possible because electronic components within an integrated circuit can be miniaturized and can be placed closer together than electronic components in a discrete electronic circuit.
Second, a given electronic circuit may exhibit superior electrical performance when implemented by an integrated circuit than when implemented by discrete parts. As was noted above, electronic components within an integrated circuit can be placed closer together than electronic components in a discrete electronic circuit. Placing electronic components closer together allows lengths of connecting electrical conductors to be reduced. Electrical conductors inherently possess parasitic elements such as resistance, inductance, and capacitance. Such parasitic elements are generally proportional to conductor length and often degrade electrical performance of the electronic circuit they are a part of. Consequently, decreasing separation between electronic components generally improves electrical performance of the electronic circuit.
Third, an electronic circuit may often be implemented more economically by using an integrated circuit rather than by using discrete parts. Although integrated circuits are generally expensive to design, they can generally be economically produced in large volumes using automated processes. Additionally, an installation of an integrated circuit on a circuit board generally requires placement of a single part. In contrast, an installation of an electronic circuit implemented with discrete parts on a circuit board generally requires placement of each discrete part.
Although great strides have been made in integrating electronic components into single integrated circuits, it is not always feasible to integrate all electronic components required in a given application into a single integrated circuit. By way of example, it may not be technically feasible to integrate all required electronic components into a single integrated circuit. One potential technical barrier to integration may be that a plurality of production processes are required to produce all of the required electronic components in a given application. If one or more of the production processes are not compatible with one or more of the other production processes, it may not be possible to integrate all of the electronic components into a single integrated circuit.
A second technical barrier to integrating all required electronic components into a single integrated circuit may be that certain electronic components do not operate properly when placed in close proximity to other electronic components. For example, a precision analog circuit may not operate properly when placed in close proximity to a digital circuit. Consequently, it may be impossible to integrate the analog circuit's electronic components and the digital circuit's electronic components into a common integrated circuit.
Although it may be technically feasible to integrate all electronic components of a given application into a single integrated circuit, it may not be economically feasible to do so. By way of example, integration may not be feasible if the production processes required for integration are prohibitively expensive. Another possible reason why integration may not be economically feasible is that there may not be sufficient demand for an integrated circuit to justify an investment required to design the integrated circuit.
There are many applications that require the use of two or more integrated circuits because it is not feasible to integrate all of the required electronic components into a single integrated circuit. However, many of these applications would benefit from the advantages associated with integrating all electronic components into a single integrated circuit. Examples include applications where circuit board space is limited or high frequency applications that require close spacing of electronic components. Consequentially, what is needed is an assembly that includes at least two integrated circuits but offers some of the advantages of an assembly having one integrated circuit.